In a known gear wheel mechanism, the recesses extend across the entire front face of the gear wheel surface connecting its inner and outer surfaces. Due to the play of the bearing of the outside gear wheel, the suction and pressure sides of the gear wheel mechanism are connected, strongly influencing its degree of effectiveness. See, e.g., German D OS 29 33 493.
Another known gear wheel mechanism has axial grooves in the area of the middle pressure point in the inside housing wall. The axial grooves are connected with radial grooves in the flat housing wall and with grooves of the inside cover wall. These radial grooves open into annular spaces connected in turn with one of the bearings. The groove arrangement lubricates the top bearing by means of oil from the propulsion flow. See, e.g., German OS 19 41 641.
A known gear wheel pump has a device for preventing oil losses by leakage. The individual teeth of the pump wheels are provided with grooves on their broad side. The pump wheel body is provided with at least one concentric annular groove connected with the other grooves. The individual grooves of the teeth are connected by axial and radial bores. The grooves on the front faces of the teeth each receive a packing element. The groove arrangement causes the pressure, arising as a result of squeezing liquid, to press the packing element against the pump housing, see e.g., German PS 731 332.